The use of intrabody medical equipment, such as endoscopes, catheters, and the like, for diagnostic and therapeutic indications is rapidly expanding. To improve performance, the equipment has been optimized to best accomplish the selected purpose. As an example, endoscopes have been optimized and refined so as to provide upper endoscopes for the examination of the esophagus, stomach, and duodenum, colonoscopes for examining the colon, angioscopes for examining blood vessels, bronchoscopes for examining the bronchii, laparoscopes for examining the peritoneal cavity, arthroscopes for examining joint spaces, nasopharygoscopes for examining nasal passages and pharynx, and intubation scopes for examination of a person's airway.
Optimization of the intrabody medical devices for such therapeutic and diagnostic procedures has resulted in sterile, inexpensive disposable equipment that is used alone or with non-disposable equipment. In the field of endoscopes, a conventional endoscope 10, shown in FIG. 1, has an insertion tube 12 that is connected at its proximal end 14 to a handle or control body 16. The insertion tube 12 is adapted to be inserted into a patient's body cavity to perform a selected therapeutic or diagnostic procedure. The insertion tube 12 contains an imaging system 18 having optical fibers or the like extending along the length of the insertion tube and terminating at a viewing window 19 in the insertion tube's distal end 20. The imaging system 18 conveys an image from the viewing window 19 to an eyepiece 22 on the control body 16 or to a monitor (not shown), so the user can see into a selected body cavity during an endoscopic procedure. The endoscope 10 is described in greater detail in U.S. Pat. No. Re 34,110 and U.S. Pat. No. 4,646,722, which are incorporated by reference herein.
Disposable endoscopic sheath assemblies are used to cover the insertion tube 12 and protect it from being contaminated. Accordingly, the sheath assemblies alleviate the problem and cost of cleaning and sterilizing the insertion tube 12 between endoscopic procedures. As seen in FIG. 1, a conventional sheath assembly 24, shown partially cut away for illustrative purposes, includes a flexible, elastic sheath 26 that tightly surrounds the endoscope's insertion tube 12. The sheath 26 may also contain one or more working channels 32 that extend along the insertion tube 12 and that are adapted to receive conventional endoscopic accessories therethrough without contaminating the endoscope itself during the endoscopic procedure. The sheath 26 has a distal end portion 21 that includes an endcap 34 having a transparent window 28 positioned to cover the viewing window 19 at the insertion tube's distal end 20 when the sheath assembly is installed. The endcap 34 is formed of a relatively rigid material and is sealably secured to the sheath's distal end portion 21.
Endoscopic sheath assemblies used with insertion tubes that have a complex cross-sectional shape, such as C-shaped, often must have an endcap with a corresponding complex cross-sectional shape to snugly fit over the insertion tube's distal end 20. The complex-shaped endcap can be a costly and laborious component to manufacture for the sheath assembly. Other thin-walled components that would be required to have a complex shape if used with endoscopic sheaths or other medical devices having complex shapes may include precision detent mechanisms and short-pitched threads that are manufactured with the necessary accuracy and tolerances required for intricate-medical devices.
U.S. Pat. No. 5,443,781 to Saab teaches a method of forming a disposable sheath with an optically transparent window that is integral with the sheath. The transparent window is formed so as to maintain a thin-walled, relatively inelastic, yet flexible sheath for an optical medical instrument. Saab teaches forming the sheath by heating a sheet or film of optically transparent polymeric material until the material's viscosity is substantially reduced and the film is malleable. As shown in FIG. 2, a mandrel 35 having a relatively simply cylindrical shape is thrust into the heated film 37 causing the film to stretch and to generally conform to the mandrel's shape. As a result, the heated film 37 is formed into a closed-end sheath 39 having sidewalls 36, a flange or collar 38 at its open proximal end 40, and a closed distal end 42. The mandrel 35 is selected based upon its simple geometrical shape to define the shape of the sheath 39. Accordingly, sheaths having different shapes and sizes are formed using different mandrels with the corresponding shapes and sizes.
The sheath and technique of making the sheath as discussed in Saab, however, results in the film being heated, stretched, and then cooled to remain the shape that generally corresponds to the mandrel's simple shape. The resulting sheath is limited to having a relatively simple geometrical shape. The method of Saab does not sufficiently allow for making complex-shaped components having close tolerances.
In the design of intrabody medical devices and accessories, including optical and non-optical devices, the need for components having a complex geometry has become more and more apparent. As an example, there is a need for highly-detailed components, such as endcaps, used with more complicated endoscopes. There is further a need for precisely manufactured catheter components or the like with accurately positioned detents or close-pitched threads. Other medical devices and accessories would be benefited by inexpensive thin-walled components with close tolerance demands.